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Brian,<br>
Good job of laying it out. <br>
<br>
Now here's the part I'm missing. If as you say the grid-tied
inverter(s), either micro or string, are connected to the load side
of the inverter's transfer switch, then I presume that in "normal"
(meaning grid is up) mode, the transfer switch is configured to
allow the "protected load" (a.k.a. critical load panel or backed-up
panel) to feed directly back to the main grid panel, in order to
maintain selling to the utility. The Magnum is fed by another
breaker in the main grid panel, in order to maintain battery
charging. When the grid goes down, the transfer switch is manually
switched to allow the grid-tied inverter(s) to directly feed the
protected load panel, rather than the main grid panel. The output of
the Magnum is capable of being backfed through the AC load output to
function as a battery charger.<br>
<br>
The Magnum has to be able to input on the AC load output in order to
utilize the AC output of the grid-tied inverter(s). The grid-tied
inverter(s) can't feed the main grid panel, as they would shut off
during a grid outage. And the Magnum's AC input can't feed off of
the protected loads panel, as its output also feeds that panel and
it would then be trying to feed itself.<br>
<br>
Am I even close here? It's enough to give an aging solar bozo a
headache. I would appreciate a wiring diagram and clarification as
to how such a system would be configured. And then there's the
question of why it would even be done this way, using a
battery-based inverter only for backup and a separate inverter(s)
for grid-tie. What are the advantages to this approach over simply
using a battery-based grid-interactive inverter, such as a GVFX,
Radian or XW?<br>
<br>
Thank you,<br>
Allan<br>
<br>
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<font face="Times New Roman, Times, serif"><b>Allan Sindelar</b></font><br>
<small><a href="mailto:Allan@positiveenergysolar.com"><font
color="#000099" face="Times New Roman, Times, serif"><u>Allan@positiveenergysolar.com</u></font></a></small><font
face="Times New Roman, Times, serif"><br>
<span style="font-size: 10pt;">NABCEP Certified Photovoltaic
Installer<br>
NABCEP Certified Technical Sales Professional<br>
New Mexico EE98J Journeyman Electrician<br>
<b>Positive Energy, Inc.</b><br>
3201 Calle Marie<br>
Santa Fe, New Mexico 87507<br>
<b>505 424-1112</b><br>
<a href="http://www.positiveenergysolar.com/" target="_blank"><u>www.positiveenergysolar.com</u></a><o:p></o:p></span></font>
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<br>
On 9/2/2011 6:20 PM, Brian Faley wrote:
<blockquote
cite="mid:29F6EE1B9DE8E648A7615A315B840161C9E58B@MAGNUMMAIL.MagnumEnergy.local"
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<p class="MsoNormal"><font size="2"
color="navy" face="Arial"><span
style="font-size: 10pt; font-family:
Arial; color: navy;">Hi Allen,<o:p></o:p></span></font></p>
<p class="MsoNormal"><font size="2"
color="navy" face="Arial"><span
style="font-size: 10pt; font-family:
Arial; color: navy;"><o:p> </o:p></span></font></p>
<p class="MsoNormal"><font size="2"
color="navy" face="Arial"><span
style="font-size: 10pt; font-family:
Arial; color: navy;">I’ll try to
describe the typical AC
coupled system as well as I can.<o:p></o:p></span></font></p>
<p class="MsoNormal"><font size="2"
color="navy" face="Arial"><span
style="font-size: 10pt; font-family:
Arial; color: navy;"><o:p> </o:p></span></font></p>
<p class="MsoNormal"><font size="2"
color="navy" face="Arial"><span
style="font-size: 10pt; font-family:
Arial; color: navy;">In such a system, a
NON-grid tied battery
based inverter (i.e. Magnum MS PAE) is
connected as a backup inverter, only
supplying AC power to consumer’s loads
when the grid is down. The micro
inverter(s), or string inverters are
connected on the load side of the
inverters
transfer switch, in parallel with the
inverter output so they see AC grid
power
(when available) or inverter power when
the grid goes down. The micro inverters
/ string inverters in such a system are
called AC coupled inverters because the
point of coupling is the AC system
rather than the DC system. This allows
the battery
based inverter to provide the grid
reference to the AC coupled grid-tied
inverters when the utility power is not
present – Backup mode. In that
mode the inverter will form the
reference for the grid tied inverters
and any surplus
power supplied by the grid-tied
inverters that is not being consumed by
AC
loads will charge the battery of the
inverter. In this inverter mode, once
the battery is full, the inverter senses
it and shifts the inverter frequency
by .5hz to force the grid tied inverters
off, keeping them from exporting
power, thereby stopping the battery from
overcharging. <o:p></o:p></span></font></p>
<p class="MsoNormal"><font size="2"
color="navy" face="Arial"><span
style="font-size: 10pt; font-family:
Arial; color: navy;"><o:p> </o:p></span></font></p>
<p class="MsoNormal"><font size="2"
color="navy" face="Arial"><span
style="font-size: 10pt; font-family:
Arial; color: navy;">On a large system,
a DC diversion load is
usually added in parallel with the
battery to reduce the on/off cycling of
the
grid tied inverters, which once the
frequency shift happens, will try to
reconnect every five minutes without it.
<o:p></o:p></span></font></p>
<p class="MsoNormal"><font size="2"
color="navy" face="Arial"><span
style="font-size: 10pt; font-family:
Arial; color: navy;">Using the frequency
shift method only is
rather crude, because it essentially is
a bang/bang controller – off or
on. Its not a matter of our lack of
confidence in the approach, the question
is
do you want the battery voltage swinging
around by several volts. In a DC
diversion mode system, the surplus
energy from the grid tied inverters can
be
put to work as a useful dump load rather
than just off lining several kw of PV.
<o:p></o:p></span></font></p>
<p class="MsoNormal"><font size="2"
color="navy" face="Arial"><span
style="font-size: 10pt; font-family:
Arial; color: navy;"><o:p> </o:p></span></font></p>
<p class="MsoNormal"><font size="2"
color="navy" face="Arial"><span
style="font-size: 10pt; font-family:
Arial; color: navy;">We had a white
paper describing the AC
couple mode. I’ll see what we can do to
make it more widely available,
since the interest in such systems seems
to be increasing.<o:p></o:p></span></font></p>
<p class="MsoNormal"><font size="2"
color="navy" face="Arial"><span
style="font-size: 10pt; font-family:
Arial; color: navy;"><o:p> </o:p></span></font></p>
<p class="MsoNormal"><font size="2"
color="navy" face="Arial"><span
style="font-size: 10pt; font-family:
Arial; color: navy;"><o:p> </o:p></span></font></p>
<p class="MsoNormal"><font size="2"
color="navy" face="Arial"><span
style="font-size: 10pt; font-family:
Arial; color: navy;"><o:p> </o:p></span></font></p>
<p class="MsoNormal"><font size="2"
color="navy" face="Arial"><span
style="font-size: 10pt; font-family:
Arial; color: navy;"><o:p> </o:p></span></font></p>
<p class="MsoNormal"><font size="2"
color="navy" face="Arial"><span
style="font-size: 10pt; font-family:
Arial; color: navy;"><o:p> </o:p></span></font></p>
<div>
<p class="MsoAutoSig"><font size="3"
color="navy" face="Times New Roman"><span
style="font-size: 12pt; color: navy;">Brian
Faley<o:p></o:p></span></font></p>
<p class="MsoAutoSig"><font size="3"
color="navy" face="Times New Roman"><span
style="font-size: 12pt; color: navy;">Chief
Engineer<o:p></o:p></span></font></p>
<p class="MsoAutoSig"><font size="3"
color="navy" face="Times New Roman"><span
style="font-size: 12pt; color: navy;">Magnum
Energy<o:p></o:p></span></font></p>
<p class="MsoAutoSig"><st1:street w:st="on"><st1:address
w:st="on"><font size="3" color="navy"
face="Times New Roman"><span
style="font-size: 12pt; color:
navy;">2111 W Casino Rd</span></font></st1:address></st1:street><font
color="navy"><span style="color: navy;"><o:p></o:p></span></font></p>
<p class="MsoAutoSig"><st1:place w:st="on"><st1:city
w:st="on"><font size="3" color="navy"
face="Times New Roman"><span
style="font-size: 12pt; color:
navy;">Everett</span></font></st1:city><font
color="navy"><span style="color:
navy;">, <st1:state w:st="on">WA</st1:state>
<st1:postalcode w:st="on">98204</st1:postalcode></span></font></st1:place><font
color="navy"><span style="color: navy;"><o:p></o:p></span></font></p>
<p class="MsoAutoSig"><font size="3"
color="navy" face="Times New Roman"><span
style="font-size: 12pt; color: navy;">425-353-8833<o:p></o:p></span></font></p>
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color="navy"><span style="color: navy;"><o:p></o:p></span></font></p>
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<p class="MsoNormal"><b><font size="2"
color="black" face="Tahoma"><span
style="font-size: 10pt;
font-family: Tahoma; color:
windowtext; font-weight: bold;">From:</span></font></b><font
size="2" color="black" face="Tahoma"><span
style="font-size: 10pt; font-family:
Tahoma; color: windowtext;">
<a class="moz-txt-link-abbreviated" href="mailto:re-wrenches-bounces@lists.re-wrenches.org">re-wrenches-bounces@lists.re-wrenches.org</a>
[<a class="moz-txt-link-freetext" href="mailto:re-wrenches-bounces@lists.re-wrenches.org">mailto:re-wrenches-bounces@lists.re-wrenches.org</a>]
<b><span style="font-weight: bold;">On
Behalf Of </span></b>Allan
Sindelar<br>
<b><span style="font-weight: bold;">Sent:</span></b>
Friday, September 02, 2011
4:45 PM<br>
<b><span style="font-weight: bold;">To:</span></b>
RE-wrenches<br>
<b><span style="font-weight: bold;">Subject:</span></b>
Re: [RE-wrenches] AC
Coupling</span></font><font
color="black"><span style="color:
windowtext;"><o:p></o:p></span></font></p>
</div>
<p class="MsoNormal"><font size="3"
color="black" face="Times New Roman"><span
style="font-size: 12pt;"><o:p> </o:p></span></font></p>
<p class="MsoNormal"><font size="3"
color="black" face="Times New Roman"><span
style="font-size: 12pt;">Brian,<br>
Could you speak a bit more to this,
please? My understanding is that the
need
with a string (or, I suppose, micro-)
inverter and a battery-based inverter
is
for a way to disconnect full batteries
from being overcharged when the grid
is
down and sell is disabled. The SMA
approach is to shift frequency to
reduce
string inverter output. I thought that
the battery-based (Outback, Magnum)
approach is to use a contactor to open
string inverter AC based on voltage
(crude,
but effective). <br>
<br>
So what I understand is that the PAE
inverters shift frequency: do you mean
it
simulates the shift that a <st1:place
w:st="on"><st1:placename w:st="on">Sunny</st1:placename>
<st1:placetype w:st="on">Island</st1:placetype></st1:place>
would do? And if
so, why is a diversion load
recommended, and how is it configured
into the
system? And where can we read more
about how this is designed to work?<br>
Thank you,<br>
Allan<br>
<o:p></o:p></span></font></p>
<div>
<p class="MsoNormal"><b><font size="3"
color="black" face="Times New Roman"><span
style="font-size: 12pt;
font-weight: bold;">Allan Sindelar</span></font></b><br>
<font size="2"><span style="font-size:
10pt;"><a moz-do-not-send="true"
href="mailto:Allan@positiveenergysolar.com"><font
color="#000099"><span
style="color: rgb(0, 0, 153);">Allan@positiveenergysolar.com</span></font></a></span></font><br>
<font size="2"><span style="font-size:
10pt;">NABCEP Certified Photovoltaic
Installer<br>
NABCEP Certified Technical Sales
Professional<br>
<st1:state w:st="on"><st1:place
w:st="on">New Mexico</st1:place></st1:state>
EE98J Journeyman Electrician<br>
<b><span style="font-weight: bold;">Positive
Energy, Inc.</span></b><br>
3201 Calle Marie<br>
<st1:place w:st="on"><st1:city
w:st="on">Santa Fe</st1:city>, <st1:state
w:st="on">New Mexico</st1:state>
<st1:postalcode w:st="on">87507</st1:postalcode></st1:place><br>
<b><span style="font-weight: bold;">505
424-1112</span></b><br>
<a moz-do-not-send="true"
href="http://www.positiveenergysolar.com/"
target="_blank">www.positiveenergysolar.com</a><u1:p></u1:p></span></font>
<o:p></o:p></p>
</div>
<p class="MsoNormal"><font size="3"
color="black" face="Times New Roman"><span
style="font-size: 12pt;"><br>
On 9/2/2011 4:39 PM, Brian Faley
wrote: <o:p></o:p></span></font></p>
<pre wrap=""><font size="2" color="black" face="Courier New"><span style="font-size: 10pt;">Hi Larry, <o:p></o:p></span></font></pre>
<pre><font size="2" color="black" face="Courier New"><span style="font-size: 10pt;">Magnum MS PAE inverters do indeed shift the inverter output frequency<o:p></o:p></span></font></pre>
<pre><font size="2" color="black" face="Courier New"><span style="font-size: 10pt;">when the battery is full in order to disconnect grid-tied inverters used<o:p></o:p></span></font></pre>
<pre><font size="2" color="black" face="Courier New"><span style="font-size: 10pt;">in AC coupled systems. It was designed to work in conjunction with a DC<o:p></o:p></span></font></pre>
<pre><font size="2" color="black" face="Courier New"><span style="font-size: 10pt;">diversion load - which is recommended if the system is larger than a<o:p></o:p></span></font></pre>
<pre><font size="2" color="black" face="Courier New"><span style="font-size: 10pt;">couple panels.<o:p></o:p></span></font></pre>
<pre><font size="2" color="black" face="Courier New"><span style="font-size: 10pt;"><o:p> </o:p></span></font></pre>
<pre><font size="2" color="black" face="Courier New"><span style="font-size: 10pt;">Regards,<o:p></o:p></span></font></pre>
<pre><font size="2" color="black" face="Courier New"><span style="font-size: 10pt;"><o:p> </o:p></span></font></pre>
<pre><font size="2" color="black" face="Courier New"><span style="font-size: 10pt;">Brian Faley<o:p></o:p></span></font></pre>
<pre><font size="2" color="black" face="Courier New"><span style="font-size: 10pt;">Chief Engineer<o:p></o:p></span></font></pre>
<pre><font size="2" color="black" face="Courier New"><span style="font-size: 10pt;">Magnum Energy<o:p></o:p></span></font></pre>
<pre><st1:street w:st="on"><st1:address w:st="on"><font size="2" color="black" face="Courier New"><span style="font-size: 10pt;">2111 W Casino Rd</span></font></st1:address></st1:street><o:p></o:p></pre>
<pre><st1:place w:st="on"><st1:city w:st="on"><font size="2" color="black" face="Courier New"><span style="font-size: 10pt;">Everett</span></font></st1:city>, <st1:state w:st="on">WA</st1:state> <st1:postalcode w:st="on">98204</st1:postalcode></st1:place><o:p></o:p></pre>
<pre><font size="2" color="black" face="Courier New"><span style="font-size: 10pt;">425-353-8833<o:p></o:p></span></font></pre>
<pre><font size="2" color="black" face="Courier New"><span style="font-size: 10pt;"><a moz-do-not-send="true" href="mailto:bfaley@magnumenergy.com">bfaley@magnumenergy.com</a><o:p></o:p></span></font></pre>
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